We need a move() function that works across filesystems.  I don't care if it's thread-safe.  Rename() on my system used to do this until version 4.04pl1.  Now my scipts are broken.  (I'm sure I'm not the only one.)

This should work for the simplest case (where both $src and $dest are regular files):

function move($src, $dest)
{
    $srcstat = stat($src);
    $deststat = stat(dirname($dest));

    if($srcstat[1] == $deststat[1]) {
        $rc = rename($src, $dest);
    } else {
        $rc = copy($src, $dest);
        if($rc) {
            $rc = (unlink($src) == 0);
            if( !$rc) unlink( $dest);
        }
    }
    return $rc;
}